Not strange. The current does not pass through the chip. It passes through a shunt resistor and the voltage over the resistor is measured by the chip. The reason for current through either input being "visible" is the common design of many multimeters.
Imagine two resistors in series, one 0.1 ohm and one 99.9 ohm. The 0.1 ohm resistor is connected between COM and mA. The 99.9 ohm between mA and A. The chip measures the voltage over both resistors. If mA is used the the effective shunt resistor is 100 ohm. If A is used then the effective shunt resistor is 0.1 ohm. In this case the 99.9 ohm resistor will be in series with the chip input, but that doesn't matter as its impedance is much higher than 99.9 ohms. More expensive multimeters solve this problem by sensing what input is used and beep if selected function and input doesn't match, or physically block the inputs by sliding in a shutter over the non-matching input.
Thank you Glarsson.
Last time I touched a multimeter was many years ago, a cheap Radio Shack meter I used as a teen.
I recently took an interest in electronics again after watching a bunch of EEVBLOG and related videos on Youtube. I decided to start building up equipment for my own bench with a few pieces of equipment, and begin at first with lower cost equipment, hoping to upgrade later if I decide to stick to this hobby. For meters, I purchased the Aneng rebrand and most recently, the CE MS8301B in the pics.
As you saw above, I was fooled by the terminal layout. Intuitively I moved the leads out of the Voltage slot, to the Amps slot to measure current. They even marked the indicators yellow to match the yellow labeled slot. Nice! So I thought... I even got readings in A, mA, and uA settings... must be working!
But no... mA, uA readings were off by 100x and 10,000x. I thought this must be a bug... and potentially a dangerous one.
So I decided to post here, only to discover my mistake after carefully examining the small print on the input markings... ? What, I measure Volts and amps (mA, uA) from the same input?
So begain this thread.
And now, after input from all the folks smarter than me above, I have more questions/concerns.
1. Is it this a common design, to have the Voltage input shared with the amps input (mA, uA in this case). I'd imagine you'd easily blow the 400mA fuse if you're measuring voltage and change the dial to the A.
2. Do you think the yellow A, uA and mA markings that match the yellow Amps input misleading? Surely misled me, and I'd imagine many others as well, especially Home Depot DIY shoppers.
3. I'm thinking this is a safety flaw. I think this is potentially dangerous, especially for amateur home DIYers trying to fix electrical things, and getting fooled into thinking something is outputting 10mA when in fact its 1A, or worse if you're in the uA setting. What do you think? Or is this normally accepted and a non-issue in the electrical/electronics test equipment industry?
Thank you!
Sam